hi there,
yes, i did some more experimenting too and patched that so called "library" too. also figgured that lowercase problem lately since it works with numbers and if called with a decimal value instead of a "charakter".
that toupper(*str++) patch looks nice in simple! i love it.
ill add that to my version and re-submit it to the developer.
but even we now managed it to work, to me this "library" is a shame. a user, especialy an arduino user is not supposed to "fix a library first" before first use.
thats up to hackers, coders and admins 
in my version i replaced the requirement of a PWM Pin for speaker output with the tone() function. is already send to the author.
hopefully he will add all the stuff we commited soon.
greets
Axel